Silver alloy



Patented Nov. 24, 1936 PATENT OFFICE SILVER ALLOY Childress B. Gwyn,Jr., Indianapolis, Ind., assignor, by mesne assignments, to P. R.Mallory & 00.. Inc., Indianapolis, Ind., a corporation of Delaware NoDrawing. Application April 12,1934, Serial No. 720,251

5 Claims. (01. 75-1 13) LThis invention relates to a silver alloy foruse as a replacement for pure silver and for uses to which previouslyknown silver alloys have been employed, of which may be mentionedparticu- 5 larly uses for the alloy of the present invention inconnection with silverware and electrical contacts.

Alloys, of which silver is an ingredient, have been utilized heretoforefor'such purposes as electrical contacts, silverware, coined silver,etc.

The alloys of the prior art including silver as I the principalingredient have not proved entirely satisfactory for certain of theuses, particularly as electrical contacts. For that particular use,

15 the present alloy is desirable not only because of its uniformelectrical conductivity, but also for I its arc snufiing properties,together with its resistance to mechanical deterioration, itsanticorrosive properties, as well as its desirability 'as 20 an alloywhich is conveniently manufactured and not prohibitive in cost.

The present invention seeks to accomplish the .fulfillment of theforegoing requisites, and to obtain an alloy of improved and desirablenature 5 conducive to simplicity of manufacture and mass production.

With these and'other objects in view, which will be more apparent as thedescription progresses, reference will now be had to the pre- 30 ferredingredients of the alloy and mode of manufacture.

The alloy of the present invention is basically silver with additions ofcopper, cadmium and cobalt. In the formation of the alloy, it ispreferable to provide a composition of the materials above specified inthe following proportion by weight: i

r Parts 40 Silver '70 to 80 Copper 12 to 6 Cadmium 8 to 18 Cobalt 2 to 1These several ingredients in the proportions named are melted togetherand allowed to cool, preferably being agitated to obtain a thoroughmixture of the molten mass and a final homogeneous solid alloy, Theresultant alloy has 50 been found to head very readily when upset intocontacts and to be recognized as having a most desirable ductility andtenacity. It may also be readily polished and will retain the shine orlustre. Its use'in silverware as well as its de- 55 sirability as areplacement for coin or fine silver .cally active atmospheres with myimproved alloy 10 show marked improvement over the fine, and coin silverand other silver alloys of the prior art.

Practically no sulphide coating will form on my alloy in atmospheres ofsulphur dioxide, ofammonium polysulphide, etc.

The alloy of the present invention furthermore has been proved to havefar superior arc snufiing properties than any known silver alloy of theprior art, and even superior to the use of either cadmium or cobaltalone or either cadmium or 00- balt alloyedwith silver for that purpose.This superiority over cadmium and cobalt alone is of even greaterimportance when it is appreciated that the inherent electricalresistance of cadmium is 7.54 micro-ohms per cubic centimeter at C. andthe electrical resistance of cobalt is 9.80 micro-ohms per cubiccentimeter at.20 C. whereas tests of the present alloy indicate anelectrical resistance of only 3.98 micro-ohms per cubic centimeter at 20C. When it is considered that pure silver has an electrical resistanceof 1.59 micro-ohms per cubic centimeter at 20 0., it will be obviousthat the resistance of the alloy approaches that of pure silver, beingincreased thereover not enough to be detrimental in the use of the alloyfor contact purposes. While my alloys have been manufactured utilizingthe proportionate number of parts specified as the respective limits ofthe several ingredients as listed above, it is to be understood that myinvention is not necessarily confined to the particular proportionsrecited nor to the exclusion of other ingredients. Tests have shown,contrary to what might be expected upon cursory consideration, that theuse of the twelve parts 5 of the copper gives a harder alloy than theuse of six parts of copper. It may also be stated in passing, that analloy comprising 18 parts of silver, 12 parts of copper, 8 parts ofcadmium, and 2 parts of cobalt results in an'alloy having approximately10.13 density and the utilization of 75 parts of silver, 6 parts ofcopper, 18 parts of cadmium and 1 part of cobalt results in an alloyhaving an approximate density of 10.048. I have found it desirable, inany event, to maintain a. proportion of silver and other ingredients ofthe alloy such that the total of the cadmium and/or copper, and/orcobalt shall not exceed 25% of the total. Furthermore, the percentageof. copper and of cadmium should each preferably be in excess of thepercentage of cobalt but in any event, the sums of the percentages ofcopper and cadmium must exceed the percentage of cobalt and preferablyvary materially so.

The alloy has been found to be particularly useful and serviceable asvoltage, cutout, and current relay contacts used in conjunction withinternal combustion engines, as electrical horn relay contacts, and ascontacts used with electrical (resistance type) welding machines. Theseuses are in addition to-its superiority when used for silverware,silverware refinishing and replacements. In addition, this alloy makesan excellent easy solder for joining together silver and/or silveralloys.

Any deviation from the percentage of the alloying constituents asdetailed above is not to be construed as a departure from the scope ofmy invention as it is entirely possible that I may desire to vary one"or more of the above constituents in order to obtain desirablecharacteristics for other or varied uses not detailed above,

or for special circuit or arcing characteristics,

and more particularly for definite fusing or nonfusing characteristicsunder given electrical conditions.-

Having thus described my invention, I claim: 1. An alloy consisting of'70 to 80 parts of approximately 10 silver, 6 to-12 parts of copper, 8to 18 parts of cadmium and 1 to 2 parts of cobalt.

2. An alloy consisting of about 78 parts of silver, 12 parts of copper,8 parts of cadmium and 2 parts of cobalt.

3. An alloy consisting of about parts of silver, 6 parts of copper, 18parts of cadmium and l part of cobalt.

4. An alloy consisting substantially entirely of 6 to 12 parts copper, 8to 18 parts cadmium, 1 to 2 parts cobalt and 70 to parts silvercharacterized by superiority of arc-snuffing ability over the materialscadmium, cobalt, cadmiumsilver alloys and cobalt-silver alloys, furthercharacterized by greater resistance to sulfide corrosion than finesilverand coin silver, and still further characterized by an electricalresistance of about 3.98 micro-ohms per cubic centimeter at 20 C. and bya density of approximately 10 grams per cubic centimeter.

5. An electrical contact composed substantially entirely of 6 tov 12parts copper, 8 to 18 parts cadmium, 1 to 2 parts cobalt and '70 to 80parts silver characterized by superiority ofarcsnufllng ability over thematerials cadmium, cobalt, cadmium-silver alloys and cobalt-silveralloys, further characterized by greater resistance to sulfide corrosionthan fine silver and coin silver, and still further characterized by anelectrical resistance of about 3.98 micro-ohms per cubic centimeter at20 C. and by a density of grams per cubic centimeter.

CHILDRESS B. GWYN, JR.

